Â Â Â The Determine of the Mashad Bioclimatic Condition Base on Hourly Data Â Â Â R. Esmaili, M. Montazeri Â Received: July 10, 2011/ Accepted: February 12, 2012, 55-59 P Â Â Â Â Â Extended Abstract Â 1-Introduction [1] Â Humans have been aware that weather and climate affect health and well being. Hippocrates, 2.500 years ago, wrote about regional differences of climate and their relationship to states of the health (matzarakis, 2007). Â In the several decades past, heat balance models of the human body have become more and more accepted in the assessment of thermal comfort. The basis for these models is the human energy balance equation. One of the first and still very popular heat balance models is the comfort equation defined by Fanger (1972). Â Bioclimatology data applied to the planning for architect, health and medical, exercise and tourism and vacations Climate-comforting conditions usually are expressed by indexes which a series of meteorological, human and environmental factors have been played a role in, and the possibility of comparison among different places is provided by several thermal indices such as Predicted Mean Vote (PMV), Physiologically Equivalent Temperature (PET) and Standard Effective Temperature (SET*) may be calculated for the assessment of human bioclimate in a physiologically relevant manner as shown in several applications (Matzarakis et al., 1999 Blazejczyk, Matzarakis, 2007 Â etc). All indices have the known grades of thermal perception for human beings and physiological stress (HÃ¶ppe, 1999). PET is defined as a certain air temperature related to fixed standard indoor conditions at which the heat balance of the human body is maintained with core and skin temperature equal to those under the conditions being assessed. Â .In this research, PET index has used for hourly bioclimatology assessment (06, 12 and 16 UTC) in the Mashhad city. This city is the second population city and religious capital in Iran that located to the north east in Iran. Â Â 2- Methodology Â In this research, great and population Mashad city have been selected for investigations comfortable climatic condition. We have used from The PET index in scale hourly time (06, 12 and 16 UTC) from 20 years period (1988-2007).Â Â The pet index derived the Munich energy balance model for individualsâ (MEMI) (HÃ¶ppe 1993) is such a thermo-physiological heat balance model. It is the basis for the calculation of the physiologically equivalent temperature (PET).Â Â In detail the MEMI model is based on the energy balance equation (9.1) for the human body: Â M +W + R +C + E D + E Re + E Sw + S = 0Â Â The individual heat flows in Eq. 9.1, are controlled by the following meteorological parameters (Verein Deutscher Ingenieure 1998 HÃ¶ppe 1999): Â â Air temperature: C, Ere â Air humidity: ED, ERe, ESw â Wind velocity: C, ESw â Mean radiant temperature: R Â Thermo-physiological parameters are required in addition: Â â Heat resistance of clothing (clo units) â Activity of humans (in WattÂ Â The following assumptions are made for the indoor reference climate: Â â Mean radiant temperature equals air temperature (Tmrt = Ta).2â Air velocity (wind speed) is fixed at v = 0.1 m/s. 3â Water vapor pressure is set to 12 hPa (approximately equivalent to a relative humidity of 50% at Ta = 20Â°C). Â In this research, the calculations of PET index have been done using Reymen 2.1 software. Addition of Bioclimatic assessment (climate comfort, heat stress and cold stress) calculated frequency physical event (contain precipitation, frost, storm â¦) and aesthetic event(cloudy, sunshine and ...) that effect on the comfort climateÂ Â Â 3- Discussion Â According to the obtained result, bioclimatic condition in Mashhad is very deferent in the through year. Though Mashhad experienced extreme cold stress during the winter season, never the less in the June and July was very heat stress. Â Comfortable climate period for 9:30 and 15:30 local time in Mashhad is short and located in the second separated period in the early spring and autumn .however the first period is longer than the second period. Â During to the hours study, the most of the comfortable climate condition has been done with 59 frequency in to 21:30 hour. Â In addition, the number of comfortable climate calculated for 9:30, ,15:30 and 21:30 local time respectively is 38, 46 , 59 days . the most of the cold stress frequency recorded with 44 percent (160 day) in the 21:30 hour and 9:30 with 24 percent of frequency that is located to the second grade. Â And the lowest month index in annual curve is occurred on 21:30 hour that is located in the below of curves (9:30, 15:30 and daily curves). This deferent is great in summer season (approximate 10 Â°C) . Â Â 4- Conclusions Â According to the obtained results of this research, the comfortable climate period in Mashhad for 09:30 and 15:30 local time is short and located in the second separated period in the early spring and autumn. Â totally of the comfortable climate days (18